This invention relates to processes for the preparation of esters and, more particularly, to the one-step preparation of alkyl nonadienoate esters by the reaction of 1,3-butadiene, carbon monoxide and alkanol in the presence of a palladium-containing catalyst.
The reaction of monoolefins and conjugated diolefins with carbon monoxide and alkanol to provide an alkyl ester is well known. Numerous catalysts have been used or proposed for this synthesis including bis(triphenylphosphine) palladium chloride as in U.S. Pat. No. 3,437,676; a palladium complex such as palladium diacetate with an aromatic phosphine such as triphenylphosphine as in U.S. Pat. No. 3,530,155, Japanese Pat. No. 72/37,934, Tsuji, et al., Tetrahedron 28, 3721 (1972) and Billups, et al., J. C. S. Chem. Comm., 18 (5), 1067 (1971); palladous chloride, cupric chloride and triphenylphosphine as in U.S. Pat. No. 3,530,168; palladium halide in molten tetrahydrocarbylammonium or phosphonium trihalostannate (II) or trihalogermanate (II) salts as in U.S. Pat. Nos. 3,657,368, 3,832,391, 3,968,133, 4,038,208 and 4,042,530; palladium salt complexed with a phosphine ligand such as palladium dichloride bis(triphenylphosphine) in the presence of a tin cocatalyst or promoter such as stannous chloride dihydrate as in U.S. Pat. No. 3,700,706; the palladium complex [PdCl.sub.2 (triphenylphosphine).sub.2 ](C.sub.6 H.sub.4 Cl.sub.2).sub.x as in U.S. Pat. No. 3,723,486; compounds of the formula (L).sub.2 MXY wherein L is a phosphinite, phosphonite, thiophosphinite, or dithiophosphonite ligand, M is palladium and X and Y are chloride, bromide, iodide, various substituted and unsubstituted alkyls and aryls, cyano, SnCl.sub.3, isocyanate, thiocyanate, aroyl and lower perfluoroalkyl groups as in U.S. Pat. Nos. 3,776,929 and 3,906,615; zerovalent palladium phosphine complex with or without added catalyst activator (additional phosphine) as in U.S. Pat. No. 3,780,074 and, ligand-stabilized platinum (II) catalyst complexed with excess Group IV-B metal halide, the ligand being selected from Groups V-B and VI-B of the Periodic Table as in U.S. Pat. No. 3,819,669. U.S. Pat. Nos. 4,124,617 and 4,172,087 each describes a one-step reaction of a conjugated aliphatic diene, alkanol and carbon monoxide in a nitrogen-containing tertiary base and in the presence of a palladium salt/tertiary phosphorus-containing donor ligand as catalyst to provide an unsaturated aliphatic ester derivative thereof. Other catalyst compositions which have been disclosed for use in the aforedescribed synthesis include a combination of palladium diacetate, palladium chloride/triphenylphosphine complex and additional triphenylphosphine as in Japanese Pat. No. 73/25,169; and, palladium diacetate and amino-substituted phosphine as in Japanese Pat. No. 76/149,206.